Mesh cathode for electron tubes

ABSTRACT

A mesh cathode comprising a tubular mesh grid formed of electron-emitting wires; the tubular grid having one end portion thereof fastened to an annular heating current supply terminal and having the other end portion thereof attached to a cap which is supported on a rod disposed coaxially of the tubular grid. The rod and the cap cooperate to form a second heating current supply terminal. The cap comprises a plurality of laminar members each having a plurality of arms extending radially outwardly from a centrally disposed hub having an aperture therethrough for fittingly engaging the supporting rod. The laminar members are arranged with the arms in a staggered pattern relative to each other.

llitd atent [72] Inventor Wilhelm Bertelsmann Berlin, Germany [21] ApplNo 758,059 [22] Filed Sept. 6, 1968 [45] Patented Feb. 2, 19711 [73]Assignee Siemens Alttiengesellschait Berlin and Munich, Germany acorporation of Germany [32] Priority Sept. 8, 1967 [33] Germany [31] P16 14 598.5

[54] MESH-l (IATHODE FOR ELECTRON TUBES 9 Claims, 8 Drawing Figs.

[52] US. Cl

[51] Int. Cl

[50] Field at Search [56] References Cited UNITED STATES PATENTS2,521,682 9/1950 Backer et al 2928978 3/1960 Morton PrimaryExaminer.lohn W. Huckert Assistant Examiner-Andrew J. JamesAttorney-Hill, Shennan, Meroni, Gross & Simpson ABSTRACT: A mesh cathodecomprising a tubular mesh grid formed of electron-emitting wires; thetubular grid having one end portion thereof fastened to an annularheating current supply terminal and having the other end portion thereofattachcd to a cap which is supported on a rod disposed coaxially of thetubular grid. The rod and the cap cooperate to form a second heatingcurrent supply terminal. The cap comprises a plurality of laminarmembers each having a plurality of arms extending radially outwardlyfrom a centrally disposed hub having an aperture therethrough forfittingly engaging the supporting rod. The laminar members are arrangedwith the arms in a staggered pattern relative to each other.

0 1 I it] n MESH CATHODE FOR ELECTRON TUBES BACKGROUND OF THE INVENTIONl. Field of the Invention This invention relates to mesh cathodes forelectron tubes of high capacity, and more particularly refers totransmitter tubes wherein the mesh cathode comprises a tubular mesh gridformed of electron-emitting wires having one end portion thereoffastened to an annular heating current tenninal and having the other endportion thereof attached to a cap which is supported on a rod disposedcoaxially of the tubular grid.

2. Description of the Prior Art Mesh cathodes having a tubular mesh gridformed of electron-emitting wires have been proposed heretofore, andthese prior art devices have been formed with one end portion of thetubular mesh grid attached to an annular heating current supply terminaland with the other end portion thereof attached to an elastic holdingmeans for longitudinally tensioning the tubular grid to give the same aninherent stability without additional struts or supporting members.These prior art devices had one end portion of the tubular mesh gridattached to the elastic member to compensate for the heat expansion ofthe grid which occurred during the operation of the cathode. Such aprior art device is disclosed in German Pat. No. 839,225.

Furthermore, British Pat. 987,461 discloses one embodiment of anelastic-holding member for a mesh cathode, and in particular the meshcathode disclosed therein includes an elastic cap secured to a supportbar extending coaxially of the mesh cathode and forming one of the twoheating current supply terminals of the cathode. In this particularprior art device, the cap is generally formed with a spiderlikeconfiguration, and in particular includes an annular disc fastened tothe central support rod and interconnected by means of a plurality ofradially extending arms to a ring which seals the upper end portion ofthe tubular mesh cathode. The legs of this elastic member are firstpulled downwardly and then bent upwardly at their terminal end portions.

Mesh cathodes of the type described hereinabove and including an elasticsupport member have the inherent problem of balancing the requiredelasticity with the required electrical conductive properties totransmit sufficient heating current from the central support bar to thetubular mesh grid. To provide adequate elasticity, the radiallyextending arms of the spiderlike support member are necessarily made asthin as possible. It should be understood, that the small cross sectionof the legs resulting from the elasticity requirement leads to animpractically high electrical resistance to the heating current supply.None of the mesh cathodes proposed heretofore have included an elasticsupport member having both adequate elasticity and sufficiently lowelectrical resistance.

To overcome the problem mentioned hereinabove, some prior mesh cathodeshave been formed with a substantially inelastic cap member havingsufficient electrical resistance properties and with the tubular meshgrid portion having a certain amount of elasticity. To provide thetubular mesh grid with elasticity, it has been proposed to weld onlypart of the intersecting points of the electron-emitting wires. However,welding together only part of the intersecting points of theelectron-emitting wires adversely affects the stability of the tubu- Iarmesh grid, and therefore adversely affects the life expectancy of themesh cathode.

SUMMARY OF THE INVENTION A mesh cathode, constructed in accordance withthe present invention, includes a tubular mesh grid formed ofintersecting, electron-emitting wires with one end portion of thetubular grid fastened to an annular heating current supply terminal andwith the other end portion thereof attached to an elastic cap membersupported by a rod disposed coaxially of the tubular mesh grid. The rodand the cap cooperate to form the second heating current supplyterminal. Also, the cap comprises a plurality of laminar members eachmember having a plurality of arms extending radially outwardly from acentrally disposed hub which has an aperture therethrough for fittinglyengaging the support rod. The laminar members are arranged in astaggered pattern relative to each other. Furthermore the terminal endportion of each radially outwardly extending arm is substantially bentupwardly to provide a particylindrical surface for engaging a ringmember which interconnects the several arms of the laminar membersthereby to hold the same in an assembled relationship. Desirably, thelaminar members are not in direct face to face contact, but instead areseparated by a foraminous member.

In this manner, a cap member for a mesh cathode is provided which hasboth the required electrical conductivity to supply the grid withsufficient heating current and the required elasticity to protect thetubular mesh guard against extreme deformations which occur during theoperation of the cathode. A cap portion formed in accordance with thepresent invention presents a relatively large cross section to providethe necessary low electrical resistance while also permitting thelaminar members to be kept as thin as is practical to provide thedesired elasticity. The elasticity of the cap member is increased byinterposing foraminous discs between the individual laminar member.

Thus, the present invention provides an elastic cap member having allthe necessary requirements to permit the use of a tubular mesh gridhaving the electron-emitting wires mechanically interconnected at allthe points of intersection. Although, the present invention ispreferably utilized with a tubular mesh grid having each intersectingpoint mechanically interconnected, it should be understood, that the capof the present invention may be utilized with a mesh grid having onlypart of its intersecting points mechanically interconnected.

Therefore, it is the primary object of this invention to provide a meshcathode including a tubular mesh grid having one end portion thereofattached to an annular heating current supply terminal and having theother end portion thereof attached to an elastic cap member support-edon a rod disposed coaxially of the tubular mesh grid, wherein theelastic cap member provides both the required elasticity and therequired low electrical resistance to supply a sufficient heatingcurrent to the grid.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, forminga part of this specification and in which like reference characters areemployed to designate like parts throughout the same;

FIG. 1 is a longitudinal sectional view of a mesh cathode embodying thefeatures of the present invention;

FIG. 2 is a schematic view illustrating the material from which thetubular mesh grid of the present invention is formed;

FIG. 3 is a top plan view of the cap member of the present invention;

FIG. 4 is an enlarged sectional view of the cap member illustrating theportion enclosed within the circle designated as IV in FIG. 1;

FIG. 5 is a top plan view of one of the laminar members which form thecap illustrated in FIG. 3;

FIG. 6 is a plan view of one of the foraminous spacer member;

FIG. 7 is a top plan view of a special laminar member utilized to fillin the residual angular area left by the staggered relationship of theother laminar members; and

FIG. 8 is a sectional view of an arm portion of a cap memberillustrating an alternative configuration and taken on a line asindicated byline VIII-VIII of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings,there is shown a tubular mesh grid 1 formed of a plurality ofelectron-emitting wires arranged in clockwise and counterclockwisespiral lines. As best illustrated in FIG. 2, the clockwise andcounterclockwise spiralled wires intersect as at 2 and have each pointof intersection welded together The tubular mesh grid l has one endportion thereof fastened to an annular heating current supply terminal 3and has the other end portion thereof attached to an elastic cap member4 which in turn is supported by means of a rod 5 extending coaxially ofthe tubular mesh grid. The elastic cap 4 and the rod 5 cooperate to forma second heating current supply terminal for the cathode. The elasticcap 4 further includes a centrally disposed aperture 13 having adiameter to permit fitting engagement with a reduced diameter portion asat 14 on the upper terminal end portion of the rod 5. The rod 5 has ashoulder 15 for supporting the cap 4 and further includes an externallythreaded portion on the reduced diameter portion 14 for receiving a nutto. The cap 4 is positioned between the nut I6 and the shoulder 15 withthe nut 16 retaining the cap 4 and the rod 5 in an assembledrelationship to provide an efficient electrical connection therebetween.

As best seen in FIG. 4, the elastic cap member 4 is composed of fouridentical laminar members 6 and one dissimilar laminar member E0. Thefour identical laminar members 6 are each formed with a hub portion 19and nine arm portions 7 extending radially outwardly from the hubportion. The dissimilar laminar member Itl also includes a hub portion21, but includes only one radially outwardly extending arm portion 7.Each laminar member 6 and it) is formed of a very thin sheet ofconductive metal, for example tantalum or molybdenum. The four identicallaminar members 6 and the one dissimilar member 110 are superposed oneon the other and are desirably separated from adjacent laminar membersby a disc 8 which is centrally disposed relative to the laminar membersand which includes an aperture 22 coincidental with the apertures 13 ofthe laminar members. The interposed discs 8 permit the arm members 7 and7', respectively of the laminar members 6 and 10, to flex independent ofadjacent arm members. As illustrated in FIG. 3, the laminar members 6and 10 are arranged with each radially outwardly extending arm portion 7or 7 staggered relative to the other arm portions.

Also, each arm member 7 or 7' has its outermost end portion bentsubstantially upwardly to provide a particylindrical surface as at 23.Preferably, each arm portion 7 or 7' is of an identical width, and alsois of a width such that the peripheral, particylindrical portion 23 ofeach arm portion is slightly spaced from, but not overlapping, itsadjacent arm portions. Thus, the cap member 4 is formed with a pluralityof circumferentially spaced particylindrical surfaces such as 23. Theparticyclindrical portion 23 of each arm portion 7 or 7 is welded orotherwise secured to an outer cylindrical surface formed on a retainingring 9, thereby to interconnect the laminar members at their peripheraledge portions.

To uniformly distribute the longitudinal tensioning forces exerted bythe elastic cap 4 upon the tubular mesh grid 1, it is desirable toprovide an arm portion 7 or 7' for each point of intersection present onthe tubular mesh grid at its upper peripheral edge portion. For example,the tubular mesh grid 1 illustrated in FIGS. 1 and 2 includes 37 cathodewires spiralled in a clockwise direction and an additional 37 wiresspiralled in a counterclockwise direction to form the grid mesh, therebyto provide 37 intersection points distributed about the uppercircumference of the tubular mesh grid. Therefore, the elastic capmember 4 includes 37 circumferentially spaced arm portions 7 or 7. The37 circumferentially spaced arm portions may be provided by any numberand arrangement of laminar members, but the preferred example, asillustrated in the drawings, includes four identical laminar members 6and one dissimilar laminar member 10, with the four identical laminarmembers each containing nine identical, circumferentially spaced armportions 7 and with the dissimilar laminar member containing one armportion 7 thereby to provide a total of 37 arm portions.

To obtain the correct spacing, each identical laminar member 6 has theconfiguration illustrated in FIG. 5. In particular, the radiallyextending arm portion 7a has its axis circumferentially spaced from theradially extending axis of the adjacent arm portion 7b by an angledesignated as A. The angle A is determined by dividing 360 by therequired number of arm portions, for example 37, and multiplying thatresult by the number of identical laminar members, for example four. Forthe embodiment illustrated, the angle A is approximately equal to 38, 55minutes. For the laminar member 6, as illustrated in FIG. 5, theradially extending axis of each arm portion 7 is angularly spaced fromits clockwise, adjacent arm portion by an angle equal to angle A, withthe exception of arm portion 7h relative to the arm portion 7a. Theangular spacing between the axes of arm portions 7h and 7a is greaterthan angle A to include the residual angle resulting from the differencebetween 360 and 9 X 38, 55 minutes.

In accordance with the principles of the present invention, thedissimilar laminar member 10 includes only one arm portion 7 to providethe remaining 37 arm portion for completing the cap member. The armportion 7 of the dissimilar laminar member 10 is disposed relative tothe arm portions 7 of the four identical laminar members 6 to fill in"the accumulated residual angles of the identical laminar members,thereby to provide a cap 4 having 37 equiangularly spaced arm portions 7and 7'.

With the cap member 4 constructed as described hereinabove, eachindividual intersection point around the upper peripheral edge of thetubular cathode grid 1 is individually welded to one of the arm portions7 or 7'. In this manner, a mesh cathode is provided which has an elasticcap member that provides the required elasticity and furthermoreprovides the necessary low electrical resistance to transmit therequired heating current to the tubular mesh grid.

The preferred embodiment of the invention, as described hereinabove, maybe modified to provide an increased elasticity of the cap member 4 byforming the radially outwardly projecting arm portions with at least oneparticircular impression therein as illustrated in FIG. 8 and asindicated at 29. It should be understood that the arm portion 7d, asillustrated in FIG. 8, distinguishes from the arm portion 7d, asillustrated in FIGS. 1 to 5 only by the addition of the impressions ordimples 29, and primed reference characters are employed to designatesimilar parts. To assure uniform elasticity of the arm portions, eacharm portion of a cap member 6', constructed in accordance with thisalternative embodiment, should have an equal number of impressions ordimples such as 29. Furthermore, the impressions desirably are formedwith an arcuate shape in plan view and are arranged about thecircumference of a common circle having an axis coincidental with theaxis of the cap member 6'. The impressions 29 form a point about whichthe arm portions such as 7d may bend, while not decreasing thecross-sectional area of the arm portion, such as would occur by scoringthe arm portions. Thus, the impressions such as 29 increase theelasticity without decreasing the electrical resistance properties ofthe cap member.

It has been found to be particularly advantageous to form each armportion with two impressions such as 29, one at the outer end of the armportion and one at the inner end thereof, as illustrated to FIG. 8,however, one impression such as 29, for example, at the inner end of theportion, is effective to increase the elasticity of the arm portion.

The preferred embodiment, as described hereinabove, includes a tubularmesh cathode having each point of intersection mechanicallyinterconnected, although it should be understood that the advantageousproperties of a cap member constructed in accordance with this inventionis also applicable to a tubular mesh cathode having only part of theintersecting points mechanically interconnected.

Although minor modifications may be suggested by those versed in theart, it should be understood that I wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably andproperly come within the scope of my contribution to the art.

I claim:

1. A mesh cathode for electron tubes comprising:

a tubular mesh grid formed of electron-emitting wire;

a first heating current supply terminal having an annular configurationclosing one end of said tubular mesh grid; an elastic cap member closingthe other end of said tubular mesh grid and including: several thinsheet metal laminar members superposed upon each other; each saidlaminar member formed with at least one radially outwardly extending armportions, each said arm portion being disposed in staggered relationshipto other ones of said arm portions; and a support rod disposed coaxiallyof the tubular mesh grid and supporting said elastic cap member; saidsupport rod cooperating with said cap member to form a second heatingcurrent supply terminal. 2. A mesh cathode as defined in claim 1,further comprising: disc members interposed between adjacent ones ofsaid laminar members for axially separating said laminar members.

3. A mesh cathode as defined in claims 1 and 2 further characterized by:

said tubular mesh grid formed with spirally wrapped, intersecting,electron-emitting wires providing a series of circumferentially spacedintersecting points around the upper peripheral edge of said tubulargrid; and said elastic cap member formed to provide one said arm portionfor each said intersecting point around the upper peripheral edge ofsaid tubular grid. 4. A mesh cathode as defined in claim 3; furthercharacterized by:

said electron-emitting wires forming said tubular mesh gn'd having allintersecting points thereof interwelded. 5. A mesh cathode as defined inclaims 1, and 2 further characterized by:

each said arm portion having the outermost end portion thereof bentupwardly at right angles relative to the remainder of said arm portionto provide a generally axi' ally extending peripheral portion; and

said arm portions being arranged to provide a plurality ofcircumferentially spaced peripheral portions around the circumference ofsaid cap member.

6. A mesh cathode as defined in claims 1, and 2 further characterized byeach said am portion being formed with a particircular impressiontherein with said impressions formed on a circular line concentric witha longitudinally extending axis of said laminar members.

7. A mesh cathode as defined in claims 1, and 2 further characterized bysaid electron-emitting wires forming said tubular mesh grid beingspirally wrapped with all points of intersection being interwelded.

8. in a mesh cathode for electron tubes comprising a tubular mesh gridformed of electron-emitting wire, a first heating current supplyterminal closing one end of said tubular mesh grid, wherein theimprovement comprises an elastic cap member closing the other end ofsaid tubular mesh grid and compris mg:

a plurality of thin sheet-metal laminar members superposed upon eachother in laminar adjacency;

each said laminar member having at least one radially outwardlyextending arm portion;

each said am portion being disposed in circumferentially staggeredrelationship to other ones of said arm portions; each said am portionhaving an outer free end circumferentially spaced from free ends formedon said other arm portions;

means interconnecting said free ends of said arm portions with the otherend of said tubular mesh grid;

support means disposed coaxially of the tubular mesh grid and supportingsaid elastic member; and

said support means cooperating with said laminar members to form asecond heating current supply terminal.

9. A mesh cathode as defined in claim 8, further comprising disc membersinterposed between adjacent ones of said laminar members for axiallyseparating said laminar members.

1. A mesh cathode for electron tubes comprising: a tubular mesh gridformed of electron-emitting wire; a first heating current supplyterminal having an annular configuration closing one end of said tubularmesh grid; an elastic cap member closing the other end of said tubularmesh grid and including: several thin sheet metal laminar memberssuperposed upon each other; each said laminar member formed with atleast one radially outwardly extending arm portions, each said armportion being disposed in staggered relationship to other ones of saidarm portions; and a support rod disposed coaxially of the tubular meshgrid and supporting said elastic cap member; said support rodcooperating with said cap member to form a second heating current supplyterminal.
 2. A mesh cathode as defined in claim 1, further comprising:disc members interposed between adjacent ones of said laminar membersfor axially separating said laminar members.
 3. A mesh cathode asdefined in claims 1 and 2 further characterized by: said tubular meshgrid formed with spirally wrapped, intersecting, electron-emitting wiresproviding a series of circumferentially spaced intersecting pointsaround the upper peripheral edge of said tubular grid; and said elasticcap member formed to provide one said arm portion for each saidintersecting point around the upper peripheral edge of said tubulargrid.
 4. A mesh cathode as defined in claim 3, further characterized by:said electron-emitting wires forming said tubular mesh grid having allintersecting points thereof interwelded.
 5. A mesh cathode as defined inclaims 1, and 2 further characterized by: each said arm portion havingthe outermost end portion thereof bent upwardly at right angles relativeto the remainder of said arm portion to provide a generally axiallyextending peripheral portion; and said arm portions being arranged toprovide a plurality of circumferentially spaced peripheral portionsaround the circumference of said cap member.
 6. A mesH cathode asdefined in claims 1, and 2 further characterized by each said armportion being formed with a particircular impression therein with saidimpressions formed on a circular line concentric with a longitudinallyextending axis of said laminar members.
 7. A mesh cathode as defined inclaims 1, and 2 further characterized by said electron-emitting wiresforming said tubular mesh grid being spirally wrapped with all points ofintersection being interwelded.
 8. In a mesh cathode for electron tubescomprising a tubular mesh grid formed of electron-emitting wire, a firstheating current supply terminal closing one end of said tubular meshgrid, wherein the improvement comprises an elastic cap member closingthe other end of said tubular mesh grid and comprising: a plurality ofthin sheet-metal laminar members superposed upon each other in laminaradjacency; each said laminar member having at least one radiallyoutwardly extending arm portion; each said arm portion being disposed incircumferentially staggered relationship to other ones of said armportions; each said arm portion having an outer free endcircumferentially spaced from free ends formed on said other armportions; means interconnecting said free ends of said arm portions withthe other end of said tubular mesh grid; support means disposedcoaxially of the tubular mesh grid and supporting said elastic member;and said support means cooperating with said laminar members to form asecond heating current supply terminal.
 9. A mesh cathode as defined inclaim 8, further comprising disc members interposed between adjacentones of said laminar members for axially separating said laminarmembers.